In recent years, the petroleum industry has invested heavily in the development of improved marine survey techniques and seismic data processing methods in order to increase the resolution and accuracy of seismic images of subterranean formations. Marine surveys illuminate a subterranean formation located beneath a body of water with acoustic signals produced by one or more submerged seismic sources. The acoustic signals travel down through the water and into the subterranean formation. At interfaces between different types of rock or sediment of the subterranean formation a portion of the acoustic signal energy may be refracted, a portion may be transmitted, and a portion may be reflected back toward the formation surface and into the body of water. A typical marine survey is carried out with a survey vessel that passes over the illuminated subterranean formation while towing elongated cable-like structures called streamers. The streamers may be equipped with a number of collocated, dual pressure and particle motion sensors that detect pressure and particle motion wavefields, respectively, associated with the acoustic signals reflected back into the water from the subterranean formation. The pressure sensors generate pressure data that represents the pressure wavefield and the particle motion sensors generate particle motion data that represents the particle motion wavefield. The survey vessel receives and records the seismic data generated by the sensors.
A wavefield that propagates upward from the subterranean formation and is detected by the pressure or particle motion sensors is called an up-going wavefield. Ideally, a pressure or particle motion up-going wavefield alone may be used to compute a seismic image of the subterranean formation. However, the surface of the water acts as a nearly perfect acoustic reflector. As a result, the sensors also detect a down-going wavefield created by reflection of the up-going wavefield from the water surface. The down-going wavefield is essentially the up-going wavefield with a time delay that corresponds to the amount of time it takes for acoustic signals to travel up past the streamers to the water surface and back down to the streamers. The down-going wavefield creates “ghost” effects in seismic images of the subterranean formation. Typical seismic data processing techniques use both the pressure wavefield and particle motion wavefield to capture the up-going pressure and particle motion wavefields. However, the particle motion sensor may also record low-frequency noise, such as low-frequency noise created by streamer vibrations, that contaminates seismic images produced from the up-going wavefields. Those working in the field of marine exploration seismology continue to seek methods and systems that improve seismic image quality.